The N400 Citizenship form is the application required to apply for United States citizenship, also referred to as naturalization. Permanent residents (Green Card holders) wishing to become naturalized citizens must complete this form as the first step in the naturalization process. The form is 10 pages long, and needs to be filed with the USCIS office responsible for processing N400 forms for your state. A complete list of states and processing centers is available at the USCIS website. Total filing fees of $675 are due when your N400 Citizenship form is filed. These fees are reduced for applicants over the age of 75, and waived entirely for military applicants filing under Section 328 and 329 of the INA. An accompanying document, Form M-476 (A Guide to Naturalization) provides important information about eligibility requirements and processing procedures. Form N-400 application instructions often refer to information in the Guide to Naturalization. You can view or print the complete guide from the USCIS website, and can refer to it as you complete your N400 citizenship form.